Gear lapping machine



Sept. 18, 1945. F. w, DAVIS 2,385,129

l GEAR LAPPING MACHINE Filed Sept.` 25, 1945 2 Sheets-Sheet 1 f/ 74'76 ff fd M0 sept. 1s, 1945. F, W, DAVIS 2,385,129 l GEAR LAPPING MACHINE Filed sept. 25, '1943 2 sheets-sheet 2 Patented Sept. 1.8, 1945 UNITED STATES PATENT `orrlfJE mi uSlLCm Apphcatlitngvori: 503,776

`1-0 "Claims.

This invention relates to the lapping of gears, this operation being of particular utility when the gears are to be used as impellers in pressure `pumps in order `to reduce leakage between the intermeshing gears and to'increase accuracy and to reduce noise. i

One of the methods heretofore used and known as the cramp method of lapping gears, consists in supporting the `gear to be lapped for rotation about its axis, and employs a toothed lap in mesh with the gear and which is pressed radially against the gear. The lap and the gear are then traversed axially of the gear teeth and are rotated while in mesh to produce the lapping action. A serious drawback to this method as heretofore practiced resides in the fact that should the gear periphery be eccentric to the bearing axis of the gear,- this is not corrected during the lapping operation. Under vsome conditions, also, eccentricity might even be increased by the lapping operation.

The present invention, therefore, has :for an object to so modify this method that in the fully lapped gear, concentriclty of the gear axis ,and the pitch circle of the tooth face of the gear is insured. i

This modification consists in providing a micrometer stop limiting the motion of the lap toward the work axis so that the lapping is finished with the lap at a fixed distance from the gear axis for all angular positions of the lap and gear.

A further object of this invention is to provide a gear lapping mechanism in which the pressure between the lap and-the gear is yieldable and adjustable.

Still `another object is to provide such a machine in which a lap wheel of greater width than the gear may be used and with full advantage of the greater lap wheel width.

A further object is to provide an improved fixture for supporting the gear by which the gear may have free rotation about its axis, which is adjustable accurately to parallelism with the direction of traverse so that the lapped gear will not be tapered.

Yet another object is to provide for a rapid traverse of the gear being lapped, together with a slower traverse motion of the lap, which is found to be of advantage in rapidly producing a uniform lapped surface.

A still further object is to provide for rapid traverse motion between lap and gear in line with the tooth axis, thus avoiding inertia loads on the tooth .face which 'Shape- For a more complete understanding of this inventionreference may be had to the Vaccompanywould tend to destroy the tooth ing drawings in which Figure 1 is 'afragmentary side elevation vof a machine for lapping gears accordingto the method of this invention.

Figure 2 is a front elevation of the same.

Figures 3 and 4 are detail sectional views on the correspondingly numbered section lines of Figure 1.

Figure 5 is a detail vertical sectional a larger scale on line 5-5 Aof Figure 2.

Figure 6 is a detail sectional view on line `66 of Figure 5.

Figure'7 is a view similar to a portion of Figure 5,` but showing .a lost motion take-up.`

Figure 8 is a detail sectional view to a larger scale on line l-B of Figure 3.

Figure 9 is a detail sectional view on line 8 9 of Figure 8. l g

` Figure 10 is a view similar to a portion of Figure l, but 'illustrating the use of a helical instead of a straight toothed lapped wheel.

view to Figure 1l-is a view similar to Figure'3, but

showing the position of the parts where la ping is accomplished in accordance with Figure 0.

yReferring to Figure l of the drawings, the lapping operation is shown as accomplished on a shaper somewhat modified for the purpose.4 At l is indicated the frame `of the shaper, and at `2 the reciprocating ram which is caused to move back and forth as by rotation in opposite `directions of a gear 3, the teeth of which mesh with a rack I on the shaper ram. In place of the usual tool-carrying clapper of the ram, this ram carries at its forward end avertical slide 5-mounted in ways. This slide 5 has fixed thereto a forwardly extending shaft on which is journaled a gear lap wheel 6, and also journaled on the shaft and xed to rotate with the lap 6,is 'a b'elt pulley 1 about which may be passed a vbelt 8 which also engages about a small pulley 9 of a reversible Vlow speed motor I0. This motor l0 is mounted on an arm Illa extending laterally from the slide 5, and the belt 8, as shown, is of the twisted type which engages about the pulleys Awith light friction, so that slippage may take place whenever resistance to the turning of the gear lap 6 is at all substantial.

The gear I4 to be lapped is mounted on vthe table T of the shaper in a fixture H. As shownbest in Figure 3, this xture comprises a ring shaped member l2 secured to an axially movable shaft I3 which is also mounted for angular adjustment. The gear to be lapped, and which as shown has shaft extensions I5 and I8, is supported within the ring I2, and its shaft portions I5 and I6 are arranged preferably at an angle corresponding to the helix angle of the gear relative to the shaft I3. This causes the relative reciprocation between the gear and the lap to be in line with the gear teeth so that this reciprocation does not cause the gear to be rocked back and forth with the traverse. Rotation of the gear is then produced by rotation of the lap and not by the relative reclprocation. This is advantageous, particularly where lapping is to be on the entire tooth surface, as for gears for a gear pump,y since not only does it avoid unduevwear of the. gear faces at the pitch line area. but it also permits faster traverse with corresponding faster lapping. As shown the shaft portions I5 and I5 are journaled between the cone centers 1 and I8. The cone center I1 is xed as by the pin I8.

while the cone center I8 is adjustable axially, being fixed to a block which is adjustable in ways 2| of the xture. With this arrangement of the gear within the fixture, angular adjustment of the shaft I3 will produce endwise tilting of the axis ofthe gear to be lapped, and by such angular adjustment this axis -may be brought into exact paraelism with the direction of motion of the lap 8 so that the gear in its lapped condition will be exactly straight or parallel in stead of tapering.

The angular adjustment of the shaft I3 may 1 be effected by mechanism shown best in Figures 8 and 9. To this shaft is secured as by a set screw 25, a rock arm 25, the outer end of which is shown as flattened as at 21 and ridesbetween .peripheral holes 33 for the reception of a pin or spanner wrench by which the bushing 3| may be angularly adjusted. Such angular adjustment moves the pivot bolt in an arcuate path (see full and dotted lines in Figure 8) and correspondingly adjusts the angularity of the'shaft I3, this adjustment being exceedingly ine. 'Ihe bushing 3| may be held in the bore in which it is journaled and also held in adjusted angular position, as by means of a set screw 31 engaging at its inner end in a peripheral groove 38 in the bushing.

As shown the lap wheel 8 is of greater axial length than is the gear to be lapped. 'It is given a relatively slow traverse through the traverse of the ram 2 so as to bring all portions of its axial length into operative relation to the gear being lapped, and at the same time it is desirable that the gear itself be given a more rapid reciprocation axially of the rock shaft. I3. To this end, the outer end of the shaft I3 may have secured thereto a yoke 48 having a transverse slot 4| within which rides` a roller 42on a crank pin 43. This crank pin is eccentrically disposed to a drive 'shaft 44 shown as rotated through a coupling 45 from a motor 46. The4 motor 46 is suitably supported from the table of the machine as on a bracket member 41. During this relative reciprocation between the lap and the gear to be lapped, these two parts are pressed together by a force which may be made adjustable and to a definite minimum spacing between the axis of the lap and the axis of the gear.

Means for producing the desired pressure between these parts is shown best in Figure 5. The slide 5, as shown therein, has a cap plate 5I secured thereto as by the bolts 5I and this cap plate 50 has an upwardly extended socket portion 55 having a centrally reduced diameter opening 56 through its base. Through this socket and the opening 58 extends a rod 51 threaded at its lower end. as at 58, in a member 59 carried by the forward end of the ram 2. Within the socket portion 55 and secured on the rod 51 is a flange 6I, and between this flange 5I and the base of the socket member 55 is positioned a relatively light coil spring 62. This coil spring at its upper end bears against a washer 85 beneath the flange 5I. 'Above the flange 6I is a heavier coilspring 31v which bears on a second washer 38 resting upon the flange 5I, and supported on the spring 61 is a cap member 18. This cap member 10 has a central opening 1| through which the enlarged diameter upper portion 12 of the rod 51 extends, and it is internally threaded for engagement with external threads on the socket portion 55. y

To the upper portion of the enlarged diameter part 12 there is secured, as by a set screw 15, an externally knurled indicator member 15. This member 16 has a downwardly extending rim 11 extending outwardly of the cap member 10 and cooperates with peripheral horizontal and vertical index markings 80 on the member 10 to indicate adjustment of the relative tensions of the springs 51 and 62 by reason of the turning of the rod 51 to adjust the extent of the threaded engagement of its lower end and the angular adjustment of the cap. 10. This rod 51, as shown in Figure 1, may have a hand wheel 8| at its upper end by which it may be turned.

It will be noted that the slide 5, together with the parts carried thereby, including the lap wheel, is supported by the spring 51 from the rod 51, and also that the spring 62 imparts a. downward thrust to the slide 5 and the parts carried thereby, which .actsin addition to the weight of these parts. By turning the hand wheel 8| and the cap member 10, the pressures exerted by these springs 62 and 81, respectively, may be adjusted as desired so as to determine the pressure exerted downwardly which presses the lap wheel 6 against the gear t0 be lapped. The cap member 18 may be locked in adjusted angular and axial relation with respect to the socket member 5. For this purpose it is shown as provided y with two external longitudinal slots 82 into either of which may be engaged an angle stop member 83, the base of which is slidable in a groove 84 in the upper face of the member 58 and which may be secured in adjustedlocking relation as by a screw 85 passing through a slot 85 of the stop and threaded into the member 5I).

In Figure '1 means for taking up any lost motion between the threads of the head 51 and the member 59 is illustrated. Referring to this Figure, there is threaded on the lower portion of the rod 51 a nut 90 which may be fixed in any desired position of adjustment as by a pin 8| extending therethrough andengageable in one or more sockets 92 in the upper face of the member 59. This nut is shown as recessed in its under face for the reception of a coil spring 93 which reacts between the nut 30 and the Vbe adjusted as required by pulling the pin 9| out of the socket 92 and then adjusting the nut 90 in the proper direction to adjust the tension on the spring 93 tothe amount desired, after which the pin 9| can be returned into one of the sockets 92 to hold the parts in adjusted position. The strength of the spring 93 must be sufcient to support all of the weight of the shaft 51 and all the parts carried thereby.

Means are provided, in accordance with this invention, by which the minimum approach between the lap and the axis of the gear to be lapped may be accurately nxed. Thus as the lapping proceeds under the pressure of the lap against the gear wheel, and the lap is rotated, which also rotates the gear wheel, the lapping proceeds until at least one portion reaches 'the desired minimum size at the pitch circle of the gear. The lap is then prevented from mov--v in the lapped gear oi its pitch circle and its rota-e tional axis. In order to produce this limit of motion, a micrometrically adjustable stop is em Such a stop of any suitable construction ployed.

and shown at |02 is adjustably secured to the lower end portion of a rod |00, which at its upper end is shown as threaded through the member and is provided beneath the member 50 with a lock nut I0| by which it may be secured in adjusted position.

As shown in Figure 3, the fixture Il whichv supports the gear is secured tothe top of the table T, as by bolts i05, in such an' angular relation that the teeth of the gear to be lapped where they are engaged by the teeth of the lap wheel are parallel to the line of motion of the ram 2. Since the gear itself is shown as a helical gear, the axis of the gear is then arranged at an angle to the direction of travel of the ram 2 at least approximately that of the helix angle of the gear, the lap being a spur gear.

In Figures l to 3, the gear is shown as a helical gear While the lap is a spur gear.

In Fig-V ures I0 and Il the proper arrangement where for supporting the gear to be lapped for rotation about its axis, means for supporting a gear lap of greater axial length than said gear in meshing relation to said gear, means forv reciprocating said lap axially with a stroke of predetermined 'length and rate, said length being suflicient to contact substantially the whole length of said lap with said gear, meansv for reciprocating 'said gear with a different amplitude and rate while in contact with said lap,'means for rotating said lap to thereby rotate said gear, said lap supporting means permitting said lap to move toward and from the axis of said gear, means for adjusting the pressure with which such lap may be so moved,` and means for adiustably limiting the minimum distance between said lap and said gear axis.

2. A gear lapping machine, comprising a fixture for supporting the gear to be lapped with its axis horizontal, a horizontal reciprocating head, a gear-shaped lap supported for vertical motion on said head to engage and lap said gear as said head is reciprocated, means for applying adjustable yielding pressure between said lap and gear, a stop determining .the minimum distance of asaid lap `from the axis of said gear, and means for reciprocating said head.

3. A gear lapping machine, comprising a fixture for supporting the gear to be lapped with its axis horizontal, a horizontal reciprocating head, a gear-shaped lap supported for vertical motion on said head to v engage and lap said gear as said head is reciprocated, means for applying adjustable yielding pressure between said lap and gear, a stop determining the minimum distance of said lap from the axis of said gear, means for reciprocating said head, and means for yield- Yingly rotating said lap to thereby rotate said gear.

, 4. A gear holding fixture, comprising a holder, means for journaling for krotation about its axis the gear to be lapped within said holder, means journaling said holder about an axis angularly disposed vto the axis of the gear, and means for adjusting the said gear about the journal axis of said holder.

5. A gear holding fixture, comprising a holder,

4 means for journaling for rotation about its axis of the time in one direction and part of the time in the other during a lapping operation in order to insure gear teeth symmetrical on opposite faces. This facilitates the gear being run with a mating gear in either direction with substantial equal smo'othness of operation.

From the foregoing description of an embodiment of this invention, it should be evident to those skilled in the art that various changes and modifications might be made without departing from the spirit or scope of this invention.

I claim:

1. A gear lapping machine, comprising a fixture the gear to be lapped within said holder, means journaling said holder about an. axis angularly disposed to the axis of the gear,'means for adjusting the said gear about the vjournal axis of said holder, and means for reciprocating said holder in the direction of said angularly disfposedaxis..

6. A gear holding fixture, comprising a holder,

means for journaling in said holder about the gear axis a gear to be lapped, and means for angularly adjusting said gear about an axis out of parallelism with said gear axis.

7. A gear holding fixture, comprising a support,` a gear holder, a shaft supporting said holder and journaled in said support, and means f carried by said holder supporting said gear for rotation about its axisangularly disposed to said' said holder supporting said gear for rotation about its axis angulariy disposed to said shaft, means for angularly adjusting said shaft, and means for reciprocating said shaft to thereby reciprocate said gear.

10. A gear holding fixture, comprising a support, a gear holder, a. shaft supporting said holder and journaied in said support, means carried by said holder supporting said gear for rotation labout its axis angulariy disposed to said shaft, an arm fixed to said shaft, a bushing journaied in said support, a pin eccentric-ally journaled in said bushing and a yoke carried by said pin and engaging said arm, and means faciiitatingsanguiar adjustment of said bushing to thus effect a tine adjustment of the anguiarity of said gear axis.

FRANCIS W. DAVIS. 

